There's an artist named Hanna Tuulikki who has done some interesting work relating to birdsong, particularly her piece 'Away With the Birds': to quote, "a project that explores the mimesis of birds in Gaelic song and the sensitive ecologies of the islands and highlands of Scotland. At its heart is a fifty minute composition in five movements, written for an ensemble of ten female vocalists. It is an extended soundscape in which Tuulikki weaves together fragments from nine Gaelic songs and five poems."

Link here: http://score.awaywiththebirds.co.uk